A noninvasive method has been developed for sequentially measuring left ventricular performance and myocardial segmental function following cardiac surgery in man. Radio-opaque tantalum markers are implanted in selected locations in the mid-wall of the left ventricular myocardium at the time of surgery and subsequently visualized in radiograms which are stored both on cine film and video disc recorder. A light-pen system is used to determine the coordinates of the markers from the video monitor on a frame-by-frame basis and these data are processed by a digital computer to obtain measurements of: 1) end diastolic volume, 2) end systolic volume, 3) stroke volume, 4) ejection fraction, 5) heart rate, 6) cardiac output, 7) mean segmental shortening, 8) systolic duration, 9) mean circumferential shortening velocity, 10) asynergy, 11) a ventricular velocity-synergy index, and 12) instantaneous segmental dynamics. The method provides, in essence, a "noninvasive cineventriculogram" which can be obtained and analyzed by computer as often as desired after cardiac surgery without risk or discomfort to the patient. A series of five projects are proposed utilizing intramyocardial markers in man: 1) An evaluation of sequential postoperative ventricular function and ventricular wall motion in patients having aortocoronary bypass graft surgery, 2) A study of the effects of cardiac rejection on left ventricular dynamics after cardiac transplantation and an evaluation of the effects of physiologic and pharmacologic stresses on the denervated heart, 3) An assessment of ventricular function and ventricular wall motion changes occurring as a result of pharmacologic interventions, 4) An assessment of the effects of cardiac rehabilitation, including a regular exercise program, on postoperative ventricular function, and 5) An assessment of changes in cardiac function occurring during both the early and late post-operative periods following valve replacement.